Recommendations for a new air receiver

[Julian_P]

I've a fairly old but nice 3hp belt driven compressor that sits on top of a horizontal air receiver. The tank is fairly rusty on the bottom exterior and sure to be even worse on the inside. I've recently got a bit frightened than it might explode and peel open one day as there's enough evidence on youtube to tell me that it happens on these old but newer style tanks made from steel a few millimetres thick.

Would anyone know of a good source for a new tank around the 100-150 litre mark at a reasonable cost with mounting pad so I could move the old compressor and motor over? Looks like about 5-600 quid for a whole new compressor of similar spec and I was hoping to spend rather less than that.

Thanks.

 

[Domdom]

A 47kg propane cylinder has a volume of about 120 litres and is made of good thick steel. Plus the inside has had oil in it (heavy ends) so no rust. It would make a good starting point for sure.
Need to weld on the mounting pad, weld in a nut to take the PRV and change the existing gas valve for something suited to the BSP threaded air line fittings.

 

[brightspark]

turn it over get a ball pein hammer and give it some reasonable taps with the round end if it dents easily its thin if it doesnt you will be ok rust pitting it would only pinhole and you would hear and see it if a bit of water came out. they dont explode and peel open as some folk would have u believe

 

[Julian_P]

A 47kg propane cylinder has a volume of about 120 litres and is made of good thick steel. Plus the inside has had oil in it (heavy ends) so no rust. It would make a good starting point for sure.
Need to weld on the mounting pad, weld in a nut to take the PRV and change the existing gas valve for something suited to the BSP threaded air line fittings.

That's certainly a good idea, a bit of work involved but I bet I could grind the welds off on the old mounting pad(s) and swap them over.

 

[Julian_P]

turn it over get a ball pein hammer and give it some reasonable taps with the round end if it dents easily its thin if it doesnt you will be ok rust pitting it would only pinhole and you would hear and see it if a bit of water came out. they dont explode and peel open as some folk would have u believe

Well there are a few videos on you tube showing them popped open like a balloon bursting, but I take your point. Maybe I could mount it outside the workshop so I won't be collateral damage if it does pop.

 

[brightspark]

Well there are a few videos on you tube showing them popped open like a balloon bursting, but I take your point. Maybe I could mount it outside the workshop so I won't be collateral damage if it does pop.

ive only ever had 3 rubber hoses burst at 125 psi in 50 years

 

[500e]

Meany moons ago I used 3 x 47Kg cylinders as receivers hung with taps at bottom joined by a manifold so they drained worked ok for 23 years while I gathered funds.
The compressor was an old cold room unit

 

[not done it yet]

Why change it if it is good? Regular testing is required for commercial operations - for insurance purposes. It is easy enough to test the receiver at, say 150% of SWP. I test mine to twice SWP.

 

[brightspark]

Why change it if it is good? Regular testing is required for commercial operations - for insurance purposes. It is easy enough to test the receiver at, say 150% of SWP. I test mine to twice SWP.

presumably a hydrauilic test with water

 

[Submariner1]

turn it over get a ball pein hammer and give it some reasonable taps with the round end if it dents easily its thin if it doesnt you will be ok rust pitting it would only pinhole and you would hear and see it if a bit of water came out. they dont explode and peel open as some folk would have u believe

I saw some of those images, they seemed more like the blow out my 400 Bar Steel Faber air-rifle air tank could have.
The damage looked a lot more dramatic, than one would expect from 11 Bar. But hey I am no metallurgist!
So I could be wrong.

 

[not done it yet]

presumably a hydrauilic test with water

Of course. Not many liquids that are cheaper than water! I fill with water and actually pressurise the system with a grease/oil gun.

 

[Burdekin]

Know and decent NDT techs or engineers? Get them to do a visual and get some UT wall thickness readings from any low spots. You then have a reference for any further testing you would like to do. Then just a simple calc to work out if it's ok.

A pressure vessel with pitting from internal corrosion should not catastrophically fail. What you will get is pitting which would eventually result in a pin hole leak and a release of air through that pin hole. For it to catastrophically fail due to internal corrosion a large section would need to corrode at the same rate and give all at once and I have never seen that.

 

[brightspark]

a 1 gallon oil can can withstand 50 psi and has square crimped ends before it balloons up and bursts .i did do a test on one and hid round the corner while i cranked up the pressure heres the said post testing a pressure vessel - oil can | MIG Welding Forum (mig-welding.co.uk)

 

[Julian_P]

I was involved with historic steam engine boilers once so am aware of hydraulic tests and thickness tests. The easiest way to do a DIY hydraulic test is to use a pressure washer as a pressure source with a bleed that you can progressively shut to create the required pressure. I'm not sure thickness testers would really work on material that is essentially so dam thin anyway and you tend to get false reading from the rust anyway.

So, I have cleaned the exterior surface rust and sprayed it up with some steel building green paint that I had. Put a USB camera into it and found that it is rusty (as expected) and reduced the working pressure to 8 bar and stuck it in another part of the workshop so that if it lets go then I won't be near.

As people have said, it's likely to just start hissing if the rust pits permeate right through, I once had an airtank on a 7.5 ton truck do that.